Abstract
We present the implementation of an improved technique to coherently
model the high-latitude ionospheric equivalent current. By using a
favourable and fixed selection of 20 ground magnetometers in
Fennoscandia, we present a method based on Spherical Elementary Current
Systems (SECS) to model the currents coherently during 2000–2020. Due
to the north-south extent of the ground stations used, we focus on the
model output along the 105◦ magnetic meridian. In
addition to the fixed data locations and SECS analysis grid, our
improvements involve taking into account a priori knowledge of the
large-scale current systems to improve the robustness of solving the
underdetermined inverse problem. We account for contributions from
ground induced currents assuming so-called mirror currents. An advantage
of this data set over existing empirical models of ionospheric currents
is the 1-min output resolution. High temporal resolution enables
investigation of temporal changes in the magnetic field. We present an
analysis of statistical properties of where (in magnetic latitude and
local time) and at what rate (∂Br /∂t) the radial magnetic field
component fluctuates. We show that ∂Br /∂t, which is equivalent to the
radial component of the curl of the induced electric field, is dependent
on latitude, local time, and solar cycle. Other applications of the
presented data set are also highlighted, including investigations of how
Ultra Low Frequency oscillations in ground magnetic perturbations vary
in space and time.